1. Field of the Invention
The present invention relates to a printing apparatus and a printing method, and particularly to allocation of print data to plurality of arrays of printing element such as a nozzle, or plurality of times of scans of a print head in a case that printing of one color is performed by the plurality of printing element arrays or the plurality of times of scans.
2. Description of the Related Art
Conventionally the allocation of the print data to plurality of nozzle arrays or plurality of nozzles is well known in multi-pass printing by a so-called serial type printing apparatus in which a print head scans an area of a predetermined size multiple times to complete printing of that area. For example, the allocation of the print data is performed to reduce a phenomenon of degrading quality of a print image, which is called “overflow” or “beading”. Here, “overflow” or “beading” means a phenomenon that ink droplets land in neighboring positions to be united therein, thus producing a clump of the ink droplets. When such large clump of the ink droplets is absorbed in a print medium, the clump is recognized as a relatively large dot in the printed image, bringing in image degradation such as grainy feeling.
Japanese Patent Laid-Open No. 2006-150811 describes a known arrangement for overcoming such “overflow” problem, in a so-called full line type inkjet printing apparatus. The full line type printing apparatus uses a print head in which nozzles are arrayed in a range corresponding to a width of a print medium to be conveyed. In addition, the print medium is conveyed to cause the nozzle array to be opposed to a print area of the print medium, and ink is then ejected from each nozzle to perform printing of one line. The processes are sequentially repeated to perform printing of a predetermined area of the print medium. Japanese Patent Laid-Open No. 2006-150811 describes a print head in which a plurality of such nozzle arrays are provided for one color of ink and the respective nozzle arrays of the plurality of nozzle arrays are shifted with each other in the nozzle array direction. The allocation of the print data to each nozzle array, that is, the nozzle array used for a print of each line is determined so that nozzles in the same nozzle array are not used adjacently in the conveying direction of the print medium. Consequently, for example, the nozzle for printing a pixel in the print image can belong to a nozzle array different from nozzle arrays including nozzles for printing eight pixels adjacent to the pixel in the upper-lower, right-left and slant directions. That is, the ink ejections from the eight pixels in the vicinity of the pixel are performed at timing different from that of ink ejection of the pixel. In consequence, it can reduce a possibility that “overflow” occurs caused by joining of the inks of the adjacent pixels.
The control in which the plurality of nozzle arrays are used in regard to one color and the print data are allocated to these nozzle arrays is, as described in Japanese Patent Laid-Open No. 2006-150811, relatively easy to perform in a case of the print head where the respective nozzles of the plurality of nozzle arrays are displaced from each other in the nozzle array direction. That is, as a result of the displaced nozzle arrangements, simply by determining the use order of the nozzle arrays, the allocation of the print data which is capable of reducing the joining between ink of a pixel and inks landing in eight pixels adjacent to that pixel can be made. However, even in a case of using usual nozzle arrays of which the nozzles are not displaced, by appropriately performing the allocation of the print data, for example, the joining between ink of a pixel and inks landing in eight pixels adjacent to that pixel can be reduced in the same way with Japanese Patent Laid-Open No. 2006-150811.
Incidentally, there is known an example of the print data generation in which multi-valued image data are quantized to image data having lower gradation level numbers and an arrangement pattern (dot arrangement pattern) of binary data is allocated to each gradation level of the quantized image data. In addition, in the above multi-pass print, mask processing is executed to the binary data pattern developed by the dot arrangement pattern to generate the print data for each nozzle of each scan.
In the full line type printing apparatus, however, in a case of performing printing by using plurality of nozzle arrays in regard to one ink color as described above, it is difficult to allocate the binary data developed by the dot arrangement pattern to the plurality of nozzle arrays, based upon the mask processing. More specifically, depending on the gradation level, there exists possible arrangement of binary data in such a manner as to eject ink from nozzles of different nozzle arrays at the same position (in such a manner as to overlap two or more dots). In this case, the data allocation can not be basically carried out by the mask processing.